Foreign employees holding a B, L, F, N or G permit (and Swiss citizens domiciled abroad) are taxed at source on their employment income. The employer calculates the tax using cantonal tables that already include federal, cantonal and communal tax plus, in most cantons, church tax. Quellensteuer is paid monthly and shown on the payslip.
Since 2021, foreigners earning above CHF 120,000 gross per year (CHF 500,000 in Geneva) must file a regular tax return (Steuererklärung); withholding is then treated as a payment on account. Those earning less can request a 'subsequent ordinary assessment' to claim deductions such as Pillar 3a contributions, professional expenses or alimony.
Once a permit C is granted (typically after 5 or 10 years of uninterrupted residence) or the foreigner marries a Swiss citizen / permit-C holder, Quellensteuer ends and the regular Swiss tax-return system takes over.
A French national with a B permit earning CHF 8,000 gross per month in Zurich, married with one child, pays roughly CHF 580 in Quellensteuer per month — already including federal, cantonal, communal and church tax.